1. Field of the Invention
The invention relates to a microscope, and in particular to a microscope utilizing multi-wavelength laser beams.
2. Description of the Related Art
FIG. 1a shows a conventional microscope 1 comprising a light source unit 10, a splitter 21, a splitter 22, a reflector 31, a reflector 32, a reflector 33, a frequency shifter 40, a stopper 50, a photoelectric detector 60 and probe 70. A laser beam 11 is emitted from light source unit 10, passing splitter 21 and split into a first beam 12 and a second beam 13. First beam 12 is reflected by reflector 31 toward frequency shifter 40, and split into a diffraction beam 14 and a zero-order beam 15. Zero-order beam 15 is stopped by stopper 50. Diffraction beam 14 passes reflector 32, splitter 22 and reflector 33 to photoelectric detector 60. Second beam 13 passes splitter 22 to probe 70 to detect sample 80.
When a wavelength of incident laser changes, the direction of diffraction beam of laser changes correspondingly to fail the interferometer. With reference to FIG. 1b, when laser beam 11′ with improper wavelength is projected to frequency shifter 40, a corresponding diffraction beam 16 is generated. However, the light path of diffraction beam 16 is different from diffraction beam 14. The difference in wavelength of laser beam changes the corresponding light path thereof. Diffraction beam 16 cannot be projected onto photoelectric detector 60. Thus, conventional interferometer microscope 1 only can detect a sample with a single-wavelength laser beam, not a multi-wavelength laser beam.